This invention relates to puller apparatus for removing (lifting) metal posts from the ground. The invention is especially concerned with the expeditious removal of metal fence posts from anchored positions extending into the ground.
U.S. Pat. No. 3,762,687 to E. DeRome shows a post puller apparatus that comprises two metal plates having cross-shaped holes therethrough configured to the cross-sectional shape of a metal post. The two plates can be thereby slipped downwardly on a metal fence post and then tilted at acute angles to the post axis, such that edge areas of the holes in the plates can grip side surfaces of the post. The two plates are individually attached to opposite ends of a chain that is attachable to a hook extending downwardly from a hoisting apparatus. When the hook is drawn vertically upwardly the two tilted plates act as clamps to grip the post tightly for pulling the post out of the ground.
The apparatus of U.S. Pat. No. 3,762,687 can be operated successfully. However, the patented apparatus is believed to have some deficiencies. For example, the holes in the two plates are mirror images of one another, but they are not symmetrical. This means that the plates must be installed onto a post in a certain order, and with specific surfaces of each plate facing upwardly; it is possible to install the plates incorrectly if the person fails to follow a specific procedure.
Also, with the apparatus of U.S. Pat. No. 3,762,687 the plates are susceptible to falling in an unregulated fashion downwardly along the post. It may be difficult to lower and hold the two clamping plates at specific locations on the post. If the hoisting apparatus has a limited stroke distance it may be desirable to position the clamping plates at specific locations on the post such that the stroke distance of the hoisting apparatus can be fully utilized for lifting purposes (not merely taking up slack in the chain). The patented apparatus is not believed suited to an easy and simultaneous manipulation of the clamping plates to specific locations on the post.
The apparatus of U.S. Pat. No. 3,762,687 apparently requires that the two clamping plates be in simultaneous engagement with the post and with each other before initiation of a pulling force by the hoisting apparatus. This would seem to dictate a two-man operation, i.e. one man to hold the two plates in position, and a second man to operate the hoisting apparatus. It would be desirable to have an apparatus that could be operated by one man.
The present invention contemplates a post puller apparatus that utilizes only one clamping plate, as opposed to the two clamping plates required in the apparatus of U.S. Pat. No. 3,762,687. The single clamping plate is designed so that when it is moved downward on a post it will stay in any given position to which it is moved; this adapts the apparatus for one-man operation. The lifter chain associated with the single clamping has a series of enlarged lifter rings spaced therealong, such that the hoist apparatus can be operatively engaged with any one of the lifter rings. This feature gives the apparatus some versatility as regards the type of hoisting apparatus that can be used; the hoisting apparatus can have its chain-attachment hook located at different elevations without rendering the system inoperable.